The challenge for drying and powderizing functional foods, nutraceuticals, and natural health ingredients is to efficiently produce free-flowing powdery products, while maintaining a high level of bioactive functionality of said products.
Traditionally, spray drying is a technique which has been used mainly in the food and pharmaceutical industries to produce powders from liquid solutions, suspensions or dispersions. Typically, the liquids to be spray-dried are atomized into small droplets, and fed at the top of a tall tower through which hot air is passed concurrently or counter-currently. Proper atomization of the feed is of prime importance for efficient drying.
Three basic feed devices are used extensively in the industry: (a) single fluid nozzle or pressure type, (b) two-fluid nozzle or pneumatic type, and (c) spinning disc, though other techniques such as pulse combustion or ultrasonic dispenser are also used in certain applications.
Even though such a spray drying process has successfully been used over 60 years, its economic viability is still problematic and present challenges for a daily production less than 1000 kg of powdery biomaterials, mainly due to the large size of the equipment.
Freeze drying (i.e., lyophilisation) is another well-established technique to process biological materials, pharmaceuticals, and functional foods, which can previously be frozen. Freeze dryers commonly include a freeze drying chamber, shelves in this chamber for holding the material to be freeze-dried, a condenser, a vacuum system, and fluid pipes for connecting the various freeze dryer components. Generally, the freeze dryer shelves are cooled and heated during the freeze drying cycle with cooling and heating devices. In such dryers, the water or the organic solvent within the frozen material to be processed is removed as a vapour by sublimation from the frozen material placed in a vacuum chamber. After the frozen water or the organic solvent sublimes directly to a vapour, the freeze-dried product is removed from the shelves. The freeze-dried products are usually in a crystalline form requiring a post-processing step such as milling and sieving. One of the key advantages of freeze drying is no thermally-induced product degradation such as denaturation or modification of functionality properties of the freeze-dried product.
However, there remain drawbacks for both the traditional spray drying and freeze drying processes.
For example, spray dryers generally operate at high temperature (typically 120-250° C. for heat-sensitive biomaterials). As such, the biomaterials are exposed to a high shear stress which can affect the stability of the macro and micro molecules in complex biomaterials (for example, proteins, flavonoids polysaccharides, etc.). There is also the adhesion of a dried product to the dryer walls due to their fine powder form when dry, and the stickiness phenomenon related to moisture content and material temperature. This adhesion issue adds cost for cleaning and leads to production losses. Additionally, the size of the drying chamber and the related ancillary equipment (e.g., high pressure atomizing device, powder collector, etc.) are large in size which increases the investment costs.
On the other hand, freeze dryers have long processing time (typically, from 12 to 24 hours per cycle, which translates into high operating costs) and high energy consumption (by 2 to 4 times higher than the other drying techniques). In addition, post-processing of dried products is required to obtain a desired size of the powder which also results in high investment costs (typically, from 3 to 6 times higher than spray dryers).
Therefore, there is still a need for an efficient and cost-effective drying to obtain powdery functional foods, nutraceuticals, and natural health ingredients.
There exist prior art references which disclose the use of an atomizing device or process and the use of spraying method.
For example, Canadian Patent 2,394,127 generally discloses the technique forming a hollow cone of liquid, the device comprising a housing into which a first medium in the form of a liquid to be atomized can be supplied, the housing comprising an outflow end and an insert piece with a guide end that interacts with an outflow end of the housing, thereby forming an annular outflow gap. Canadian Patent Application 2,021,970 generally discloses an air atomization paint spray gun. U.S. Pat. No. 4,361,965 generally discusses a device for atomizing a reaction mixture, said device enabling the reaction mixture to be atomized in a reactor with the aid of at least a first gas and an atomizing nozzle. U.S. Pat. No. 8,313,704 generally discloses a spouted bed device having a conical baffle which has an outside diameter that increases progressively downward, is closed at a top end thereof, and has a bottom end that is spaced apart from an inside wall of the cylinder, wherein the conical baffle is disposed at a position which is below and opposed to a bottom end of the tubular portion of the treatment zone. U.S. Pat. No. 4,896,436 generally discloses a spray drying process and the apparatus, and provides a spray drying apparatus of integration type wherein several spray drying chambers are accommodated in a common housing.
However, it will be apparent to a person skilled in the art that none of the known patents and prior art revealed in technical literature discloses all features of the present invention, inter alia, the atomizing device, a conical-cylindrical drying chamber and the use of inert carriers.